1. Field of the Invention
The present invention relates to an improvement in a semiconductor wafer processing method including a step of adhering a die-bonding adhesive film onto a back surface of a semiconductor wafer having a plurality of devices (i.e., semiconductor devices) formed thereon.
2. Description of the Related Arts
An adhesive film called a DAF (die attach film) has been previously stuck onto a back surface of a device, thereby fabricating a package such as an MCP (multi-chip package) or an SiP (system-in package), in which a plurality of semiconductor chips are stacked. In order to achieve such a configuration, there has been known a method in which an adhesive film whose shape and size are equal to those of a wafer is stuck onto a back surface of the wafer ground into a predetermined thickness, and then, the adhesive film is cut or split together with the wafer. Otherwise, there has been known a method in which an adhesive film whose shape and size are equal to those of a wafer is stuck onto a back surface of a wafer previously ground and cut into individual devices, and then, the adhesive film is cut by a blade or a laser beam.
In the former method in which the adhesive film is cut together with the wafer, the blade is readily clogged with swarf produced from the adhesive film, or burrs are produced at the adhesive film, thereby causing bonding deficiency in die-bonding. In the latter method in which the adhesive film is cut later, the wafer is previously cut into the individual devices in advance, thereby inducing a phenomenon called die shift in which the arrangement of the devices is shifted, whereby it is impossible to cut the adhesive film by the blade. Therefore, the adhesive film must be cut by a laser beam. In this case, the adhesive film is required to be irradiated with the laser beam while correcting the position in accordance with the shift of the device, thereby raising a problem of degradation of working efficiency. Even in a case in which the laser beam is irradiated to the wafer without any die shift, there is a problem that the melted adhesive film adheres to a side surface of the device or the side surface of the device also is possibly damaged by the irradiation of the laser beam.
In order to solve the above-described problems, Japanese Patent Application Laid-open (JP-A) No. 2004-266163, for example, discloses a method, in which an adhesive film is pressed with a die, to be previously cut into a shape of a device, and thereafter, a wafer is adhesively positioned at the resultant adhesive film; to be then cut.
However, a die in conformity with the shape of the device has needed to be prepared in the above-described method, and therefore, a manufacturing cost has been increased, thereby raising a problem of cumbersome preparation and maintenance of the die in a manufacture line. In addition, the thickness of the adhesive film has been required to become thinner than 10 μm to 15 μm at present. In cutting such a thin material by pressing, the level of the bottom dead center of the die (i.e., an upper die) has needed to be adjusted in the order of several μm. Such precise adjustment has not been readily performed. Additionally, the cut adhesive film may be lifted up in contact with the upper die, and therefore, there has been apprehension that the adhesive film may be peeled off from a peeling sheet serving as a mount for the adhesive film. In this manner, a considerable difficulty has been presumed in press-cutting the adhesive film in an actual manufacturing site, and further, a high facility cost has been required for fabricating a precise die or press.